1. Field of the Invention
The present invention relates to a control device for propulsion units of a vessel having a plurality of propulsion units arranged side by side, and more particularly to a control device that selectively synchronizes the engine rotational speeds of the propulsion units.
2. Description of the Related Art
There are vessels having, for example, three propulsion units such as outboard motors, stern drives, inboard-outboard motors or the like arranged at the stern. Conventionally, in a vessel of this type, a shift lever and a throttle lever are provided for each one of the propulsion units. However, it can be complicated to operate all of the shift levers and throttle levers (six in total) in addition to a steering wheel.
A recently-developed vessel has operation control units for controlling the operating conditions of respective outboard motors that are connected to each other by communication lines for transferring operating information of respective outboard motors (See Japanese Publication No. JP-A-Hei 8-200110). Also, a vessel has been developed in which the shifts and throttles of a plurality of propulsion units are operable by two control levers laterally disposed adjacent to each other. If a difference occurs between the engine rotational speeds of the engines of the right and left propulsion units when the control levers are tilted at the same angle, based for example on the engine rotational speed of the engine of the right propulsion unit, a motor in a throttle drive part is driven to adjust the throttle and thus eliminate the difference between this engine rotational speed and the engine rotational speed of the left propulsion unit. As such, the engine rotational speeds of the right and left engines are synchronized (see Japanese Publication No. JP-A-2000-313398).